Has he suffered any type of head injury recently? I am a life long moderate-to-severe stutterer but my kids are not. At least until my 14 year old son sustained a concussion last fall. He is almost fully recovered but still has his moments. Also, your pediatrician can only do so much. In our area we can get free speech evaluations from the state at our Intermediate Unit facilities. I know because I had both of my kids evaluated when they were younger when they started showing signs of a stutter. Both were fine, until recently. Now this is import: don't stop him when he is blocked. I know it will be your first instinct to tell him to stop and calm down even though I know your heart breaks hearing him speak. Wait until he stops, and he will stop. He will learn quickly. I can't remember specifics from that age but I know how it feels after 43 years. Have him read out loud but let him do it on his terms. If he gets frustrated and quits, let him. Pressure to speak will only cause him to shut down. Be there for him. If he is intuitive as you say he will adapt. As soon as this whole mess calms down you should seek help from a licensed speech therapist. I know first hand how scary this can be. Good luck.